You're assuming the day length is always 25000 ticks, which is not true if using mods to change day length. For example, I use Diurnal Dynamics to 10x the day length.
https://mods.factorio.com/mod/diurnal-dynamics

Oh, and would you mind adding a toolbar button or hotkey to toggle on/off the interface completely?

Interesting, thanks for the feedback, I will use the day length from the surface settings I think instead.

Yeah that is a good idea I can add something like that, thanks for the idea.

That should work yeah.

The day number is correct now, but some of the other stats look incorrect still.
https://i.imgur.com/rL7sZKZ.png

93% at 10:50 seems wrong.
10.1x should be 10x.